This invention relates to a hub clutch assembly mounted on each front wheel of a four-wheel drive vehicle to selectively transmit and cut off driving force between the front wheel axle and the wheel hub of each front wheel.
A part-time four-wheel drive vehicle has a hub clutch assembly mounted between each front wheel hub and the front wheel axle to selectively transmit driving force to the front wheels.
A conventional hub clutch assembly has a slide gear axially slidably mounted on the axle. By sliding the slide gear into engagement with the wheel hub, the driving mode is changed over to the four-wheel drive position. By disengaging the slide gear from the wheel hub, the driving mode changes over to the two-wheel drive position. Fluid pressure such as air pressure is used to move the slide gear between these two positions.
The arrangement in which air pressure is used to move the slide gear has a problem in that air pressure has to be maintained at all times in order to hold the driving mode either in the four-wheel drive position or the two-wheel drive position. Since air pressure is always acting on seals of the hub and the spindle, they tend to be worn quickly. Their durability is thus extremely low.
An object of this invention is to provide a hub clutch assembly in which fluid pressure is used only while the driving mode is being changed over between four-wheel and two-wheel drive positions, thereby eliminating the necessity of keeping the fluid pressure to hold the coupling members in position once the driving mode has been changed over, to improve the durability of the seal members.